1. Field
Embodiments of the present technology relate to gas valves for use in gas appliances. More particularly, embodiments of the technology involve a variable gas valve for modulating a flow of gas into a burner of a gas appliance.
2. Description of the Related Art
Gas valves are used to regulate an amount of gas fed to a gas appliance such as, for example, an oven, furnace, hot water heater, or fireplace. Gas valves have traditionally had two settings, on and off. Use of such valves causes undesirable fluctuations in appliance output. An oven set at 350°, for example, may fluctuate between 345° and 355° as the oven temperature control cycles through on at 345°, off at 355°, and then back on at 345°.
To address the problem of output fluctuation in gas appliances, variable gas valves were developed to modulate gas flow across a range of outputs instead of between an on position and an off position. Such variable gas valves enable output control systems to operate with less fluctuations than a traditional on/off type gas valve. Unfortunately, variable gas valves suffer from various problems and limitations. For example, modulating gas flow in variable gas valves affects the gas-air mixture, causing undesirable combustion of the mixture, such a “lazy yellow” flame instead of a “hard blue” flame.
U.S. Pat. No. 6,968,853 relates to a motor-operated valve for regulating gas flow, the valve being a lift-type modulating valve with a cut-off member providing a modulated flow between a minimum and maximum flow, and a safety shut-off means in the event of a locked motor rotation.
U.S. Pat. No. 6,287,108 discloses a method and apparatus for accurately and reproducibly setting a volumetric gas flow through a gas feed line to a burner nozzle of a gas-operated cooking or baking appliance as required for a desired burner heat output. A control system uses actual flow measurements from a gas flow meter and makes gas flow adjustments by means of an actuator operated valve accordingly.
U.S. Pat. No. 6,029,705 relates to a gas control valve for effecting the largest possible manipulation of visible flames in, for example, a gas-heated fireplace or similar device. A first valve includes a switch and control device facilitating operation and supervision of a burner by turning a flow of the gas on and off. A second valve manages pressure control and adjustment of the flame height by regulating a volume of gas flowing to the burner. A battery-operated, motor-driven actuator drives one of the two valves.
U.S. Pat. No. 5,979,484 relates to a safety and regulation valve including a reversible motor actuator acting on a movable device. The movable device is movable between an on position, an off position, and a plurality of intermediate positions for varying a volume of gas flow.
U.S. Pat. No. 5,458,294 provides a variable-orifice, solenoid-operated valve as a control device to meter gas flow as a function of sensed temperature and desired temperature.
U.S. Pat. No. 5,234,196 discloses a gas modulating valve for use with a gas burner. The valve accomplishes modulation through the use of two sliding plates positioned next to each other that have orifice holes that result in a reduced orifice passageway when the two plates are misaligned with each other. One of two variations disclosed discharges a gas jet directly into a mixing tube of a gas burner, while a second variation operates as an in-line gas modulating valve.
U.S. Pat. No. 4,930,488 relates to a microprocessor-controlled gas appliance comprised essentially of a computer control system and a microprocessor-actuated modulating gas valve.